It is known to apply to non woven media dots of various shapes, as well as lines and other geometric shapes. Such geometric shapes were being printed in a variety of thicknesses. The purpose of the printing application was to thicken or stiffen the material for use as a garment interlining. In other applications, dots and other shapes have been printed onto non woven, knitted and woven fabrics for the purpose of creating an abrasive or high friction surface for cleaning or gripping (hospital socks having gripping media). Importantly, the dots, shapes, or lines are typically spaced apart, allowing significant spaces between them. The materials from which the dots, shapes or lines were made included a variety of polymeric materials, often resulting from liquid emulsions of fine powders, pigments, and binders which are subsequently cured and/or polymerized on the surface of the fabric through the application of heat. Some versions can be cured through other means, including the addition of catalysts, UV, or other means.
Air filtration filters have become increasingly able to trap very fine particulates, including particles as small as sub micron in size. However, new problems have arisen that potentially affect the performance of the filter. As an example, filters using current technology can actually trap particles as small as bacteria, fungus, and mold spore. Air filters in residential and commercial applications often exist in dark, warm, moist spaces, which is an ideal environment for microbiological growth. This microbial growth in and on the air filter can cause odors which are distributed throughout the residence or business. It also actually shortens the life of the filter, with microbiological growth actually restricting airflow, leading to premature replacement. Additives may be incorporated into and onto air filtration media through several methods. One method includes mixing them into the binder of the fibers (on binder based non wovens). The problems with this method include the potential for the binder to encapsulate the additives, rendering them ineffective.
Additionally, the inclusion of the additives can adversely impact the curing of the binder resulting in poor fabric structure and filtration performance. Another method for producing non woven fabrics is the use of bicomponent fibers which have a layer of lower melt temperature polymer allowing the fibers to bond together with the application of temperature and form the non woven fabric. In this method of fabric construction, the additives must be incorporated directly into the fiber when it is extruded. The additives can be encapsulated and rendered ineffective, or the additives can actually interfere with the extrusion process, slowing production or affecting fiber quality. Similar issues result with meltblown or meltspun non woven fabrics, where the additives are incorporated directly into the fibers as they are formed. In another method of treating fabrics with additives, silane based coatings containing the additives are applied directly onto the fabrics. Several issues are associated with this method. First, the silane coatings are applied to the entire surface of the fabric, typically wetting the entire fabric, and then are cured in place. This can affect the filtration performance characteristics of the fabric, often increasing the resistance to airflow and interfering with electrostatic treatments. Additionally, this type of coating is often not compatible with porous particulate additives, effectively plugging the pores.
The present invention solves all the potential problems set forth above by using a method of printing dots, shapes or lines or other intermittent geometric shapes onto filtration media, leaving significant spacing between the printed dots, shapes, or lines. Airflow is very minimally affected versus coating the entire fabric. Additionally, the thickness of the dots, shapes, or lines can be closely controlled, allowing thicker or thinner application as required for different types of additives. The intermittent geometric shapes are applied in an aqueous latex base and then cured on the filtration media by heating, chemical reaction, U.V. curing or other known methods. The intermittent geometric shapes can be applied to the filtration media by a printing process.